Preparation, characterization. and low-temperature heat capacities of nanocrystalline TiO2 ultrafine powder

Nanocrystalline TiO2 ultrafine powders with different grain sizes have been prepared by the sol-gel method. The grain sizes and the crystalline phases have been determined, Heat capacities in the temperature range of 78-370 K have also been measured, and the polynomial equations expressing the change of heat capacity with temperature were fitted. The obtained values of the heat capacity have been compared with those of the bulk crystal from the Literature, The relations between heat capacity and the grain size of nanocrystalline TiO2 have been discussed in terms of energy. (C) 2001 Academic Press.